(a) Draw the circuit diagrams for obtaining the $\text{V} - \text{I}$ characteristics of a p-n junction diode. Explain briefly the salient features of the $\text{V} - \text{I}$ characteristics in (i) forward biasing, and (ii) reverse biasing. OR (b) On the basis of energy band diagrams, distinguish between (i) an insulator, (ii) a semiconductor, and (iii) a conductor.